1. Field of the Invention
The present invention relates to an imaging apparatus that uses X-rays and light to make a measurement on a living body, for use in the field of diagnostic instruments intended mainly for purposes of early diagnosis of disease such as cancer.
2. Description of the Related Art
A mammography apparatus is developed as a device for early detection of breast cancer and is widely used for examination for breast cancer or the like. The mammography apparatus is an X-ray machine intended solely for the breast and is capable of detecting tiny calcification developed around a tumor or a cancer cell.
A method for imaging the inside of a cloudy medium such as the breast, using light, is reported in Japanese Patent Translation Publication No. 2001-510361. The method irradiates the breast with the light, and measures the light scattered within the breast. Then, the method calculates the absorption distribution of the light within the breast, on the basis of the measured data. The method exploits, in particular, the property that blood absorbs the light intensely so as to detect a nutritional blood vessel formed around a cancer cell. A method such as Diffuse Optical Tomography (DOT) described for example in David A. Boas et al., “Imaging the Body with Diffuse Optical Tomography,” IEEE Signal Processing Magazine, Vol. 18, No. 6, pp. 57-75, (2001) is used as a method for calculating an optical absorption distribution in a living body, on the basis of measured data on scattered light.
A method intended mainly for a living body such as a small animal is developed and widely used. This method involves administering a fluorescent molecular probe or a luminescent molecular probe into the living body, and measuring a distribution thereof within the living body. The fluorescent molecular probe and the luminescent molecular probe can provide selectivity for a target molecule unusually formed by a tumor or the like. Accordingly, these probes have the merit of being capable of making a high-sensitive measurement on a tiny cancer cell. Currently, various types of fluorescent molecular probes using fluorescent proteins, fluorescent nanoparticles, or the like, or luminescent molecular probes using luciferase are developed. A method intended for purposes of detection of breast cancer, which involves administering a fluorescent molecular probe into the human body and performing imaging using DOT, is tried and reported in Hawrysz D. J. et al., “Developments Toward Diagnostic Breast Cancer Imaging Using Near-Infrared Optical Measurements and Fluorescent Contrast Agents,” Neoplasia, Vol. 2, No. 5, pp. 388-417 (30), (2001).